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import java.util.*;
import org.nfunk.jep.*;
import org.nfunk.jep.function.*;
/**
* An example custom function class for JEP.
*/
class Half extends PostfixMathCommand {
/**
* Constructor
*/
public Half() {
numberOfParameters = 1;
}
/**
* Runs the square root operation on the inStack. The parameter is popped
* off the <code>inStack</code>, and the square root of it's value is
* pushed back to the top of <code>inStack</code>.
*/
public void run(Stack inStack) throws ParseException {
// check the stack
checkStack(inStack);
// get the parameter from the stack
Object param = inStack.pop();
// check whether the argument is of the right type
if (param instanceof Double) {
// calculate the result
double r = ((Double)param).doubleValue() / 2;
// push the result on the inStack
inStack.push(new Double(r));
} else {
throw new ParseException("Invalid parameter type");
}
}
}
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